Person: García Ortega, Lucía
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First Name
Lucía
Last Name
García Ortega
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Bioquímica y Biología Molecular
Area
Bioquímica y Biología Molecular
Identifiers
20 results
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Now showing 1 - 10 of 20
Item Papel de la horquilla amino-terminal como elemento clave en la funcionalidad de las ribotoxinas de "aspergillus"(2005) García Ortega, Lucía; Martínez del Pozo, Alvaro; Gavilanes Franco, José GLas ribotoxinas son una familia de ribonucleasas, con una característica citotoxicidad y alergenicidad. En esta Tesis Doctoral queda demostrado el papel esencial que un elemento de su estructura, la horquilla amino-terminal, juega en estas funciones. Esta región es responsable del obligatorio reconocimiento del ribosoma, necesario para la posterior inhibición de la biosíntesis de proteínas en las células diana mediante su actividad ribonucleasa específica sobre dicho sustrato. Y además, contiene epítopos que participan en la inducción de la respuesta alérgica en pacientes sensibilizados a Aspergillus. La caracterización de este elemento de las ribotoxinas ha significado un paso cualitativo a la hora de comprender el mecanismo por el cual actúan estas proteínas, y abre la puerta a su posible aplicación en el ámbito clínico.Item Characterization of a new toxin from the entomopathogenic fungus Metarhizium anisopliae: the ribotoxin anisoplin(Biological chemistry, 2017) Olombrada, Miriam; Medina, Pilar; Budia, Flor; Gavilanes, José; Martínez Del Pozo, Álvaro; García Ortega, LucíaMetarhizium anisopliae is an entomopathogenic fungus relevant in biotechnology with applications like malaria vector control. Studies of its virulence factors are therefore of great interest. Fungal ribotoxins are toxic ribonucleases with extraordinary efficiency against target ribosomes and suggested as potential insecticides. Here, we describe this ribotoxin characteristic activity in M. anisopliae cultures. Anisoplin has been obtained as a recombinant protein and further characterized. It is structurally similar to hirsutellin A, the ribotoxin from the entomopathogen Hirsutella thompsonii. Moreover, anisoplin shows the ribonucleolytic activity typical of ribotoxins and cytotoxicity against insect cells. How Metarhizium uses this toxin and possible applications are on perspective.Item The ribonucleolytic activity of the ribotoxin α-sarcin is not essential for in vitro protein biosynthesis inhibition(BBA-Proteins and Proteomics, 2011) Alvarez García, Elisa; Diago Navarro, Elizabeth; Herrero Galán, Elías; García Ortega, Lucía; López Villarejo, Juan; Olmo López, Nieves; Díaz Orejas, Ramón; Gavilanes, José G.; Martínez Del Pozo, ÁlvaroFungal ribotoxins are toxic secreted ribonucleases that cleave a conserved single phosphodiester bond located at the sarcin/ricin loop of the larger rRNA. This cleavage inactivates ribosomes leading to protein biosynthesis inhibition and cell death. It has been proposed that interactions other than those found at the active site of ribotoxins are needed to explain their exquisite specific activity. The study presented shows the ability of a catalytically inactive α-sarcin mutant (H137Q) to bind eukaryotic ribosomes and interfere with in vitro protein biosynthesis. The results obtained are compatible with previous observations that α-sarcin can promote cell death by a mechanism that is independent of rRNA cleavage, expanding the potential set of activities performed by this family of toxins.Item Influence of key residues on the heterologous extracellular production of fungal ribonuclease U2 in the yeast Pichia pastoris(Protein Expression and Purification, 2009) Álvarez García, Elisa; García Ortega, Lucía; De los Ríos, Vivian; Gavilanes, José G.; Martínez Del Pozo, ÁlvaroRibonuclease U2, secreted by the smut fungus Ustilago sphaerogena, is a cyclizing ribonuclease that displays a rather unusual specificity within the group of microbial extracellular RNases, best represented by RNase T1. Superposition of the three-dimensional structures of RNases T1 and U2 suggests that the RNase U2 His 101 would be the residue equivalent to the RNase T1 catalytically essential His 92. RNase U2 contains three disulfide bridges but only two of them are conserved among the family of fungal extracellular RNases. The non-conserved disulfide bond is established between Cys residues 1 and 54. Mispairing of the disulfide network due to the presence of two consecutive Cys residues (54 and 55) has been invoked to explain the presence of wrongly folded RNase U2 species when produced in P. pastoris. In order to study both hypotheses, the RNase U2 H101Q and C1/54S variants have been produced, purified, and characterized. The results obtained support the major conclusion that His 101 is required for proper protein folding when secreted by the yeast P. pastoris. On the other hand, substitution of the first Cys residue for Ser results in a mutant version which is more efficiently processed in terms of a more complete removal of the yeast α-factor signal peptide. In addition, it has been shown that elimination of the Cys 1-Cys 54 disulfide bridge does not interfere with RNase U2 proper folding, generating a natively folded but much less stable protein.Item The ribotoxin -sarcin can cleave the sarcin/ricin loop on late 60S pre-ribosomes(Nucleic Acids Research, 2020) Olombrada, Miriam; Peña, Cohue; Rodríguez Galán, Olga; Klingauf Nerurkar, Purnima; Portugal Calisto, Daniela; Oborská Oplová, Michaela; Altvater, Martin; Gavilanes, José G.; Martínez Del Pozo, Álvaro; Cruz, Jesús de la; García Ortega, Lucía; Govind Panse, VikramThe ribotoxin -sarcin belongs to a family of ribonucleases that cleave the sarcin/ricin loop (SRL), a critical functional rRNA element within the large ribosomal subunit (60S), thereby abolishing translation. Whether -sarcin targets the SRL only in mature 60S subunits remains unresolved. Here, we show that, in yeast, -sarcin can cleave SRLs within late 60S pre-ribosomes containing mature 25S rRNA but not nucleolar/nuclear 60S pre-ribosomes containing 27S pre-rRNA in vivo. Conditional expression of -sarcin is lethal, but does not impede early pre-rRNA processing, nuclear export and the cytoplasmic maturation of 60S pre-ribosomes. Thus, SRL-cleaved containing late 60S pre-ribosomes seem to escape cytoplasmic proofreading steps. Polysome analyses revealed that SRL-cleaved 60S ribosomal subunits form 80S initiation complexes, but fail to progress to the step of translation elongation. We suggest that the functional integrity of a -sarcin cleaved SRL might be assessed only during translation.Item The behaviour of sea anemone actinoporins at the water-membrane interface(Biochimica et Biophysica Acta - Biomembranes, 2011) García Ortega, Lucía; Alegre Cebollada, Jorge; García Linares, Sara; Bruix, Marta; Martínez Del Pozo, Álvaro; Gavilanes, José G.Actinoporins constitute a group of small and basic α-pore forming toxins produced by sea anemones. They display high sequence identity and appear as multigene families. They show a singular behaviour at the water-membrane interface: In aqueous solution, actinoporins remain stably folded but, upon interaction with lipid bilayers, become integral membrane structures. These membranes contain sphingomyelin, display phase coexistence, or both. The water soluble structures of the actinoporins equinatoxin II (EqtII) and sticholysin II (StnII) are known in detail. The crystalline structure of a fragaceatoxin C (FraC) nonamer has been also determined. The three proteins fold as a β-sandwich motif flanked by two α-helices, one of them at the N-terminal end. Four regions seem to be especially important: A cluster of aromatic residues, a phosphocholine binding site, an array of basic amino acids, and the N-terminal α-helix. Initial binding of the soluble monomers to the membrane is accomplished by the cluster of aromatic amino acids, the array of basic residues, and the phosphocholine binding site. Then, the N-terminal α-helix detaches from the β-sandwich, extends, and lies parallel to the membrane. Simultaneously, oligomerization occurs. Finally, the extended N-terminal α-helix penetrates the membrane to build a toroidal pore. This model has been however recently challenged by the cryo-EM reconstruction of FraC bound to phospholipid vesicles. Actinoporins structural fold appears across all eukaryotic kingdoms in other functionally unrelated proteins. Many of these proteins neither bind to lipid membranes nor induce cell lysis. Finally, studies focusing on the therapeutic potential of actinoporins also abound.Item Characterization of a new toxin from the entomopathogenic fungus Metarhizium anisopliae: the ribotoxin anisoplin(Biological Chemistry, 2016) Olombrada, Miriam; Medina, Pilar; Budia, Flor; Gavilanes, José G.; Martínez Del Pozo, Álvaro; García Ortega, LucíaMetarhizium anisopliae is an entomopathogenic fungus relevant in biotechnology with applications like malaria vector control. Studies of its virulence factors are therefore of great interest. Fungal ribotoxins are toxic ribonucleases with extraordinary efficiency against target ribosomes and suggested as potential insecticides. Here, we describe this ribotoxin characteristic activity in M. anisopliae cultures. Anisoplin has been obtained as a recombinant protein and further characterized. It is structurally similar to hirsutellin A, the ribotoxin from the entomopathogen Hirsutella thompsonii. Moreover, anisoplin shows the ribonucleolytic activity typical of ribotoxins and cytotoxicity against insect cells. How Metarhizium uses this toxin and possible applications are on perspective.Item Fungal Ribotoxins(ELS, 2018) García Ortega, Lucía; Palacios Ortega, Juan; Martínez Del Pozo, ÁlvaroFungal ribotoxins constitute a family of extracellular ribonucleases with exquisite specificity against rRNA (ribonucleic acid). They induce apoptotic death of cells after inhibiting protein translation. Ribosomes become functionally incompetent because ribotoxins cleave one single phosphodiester bond, located at a unique and universally conserved loop, needed for elongation factors function. As secreted proteins, ribotoxins need to cross the membrane of their target cells in order to exert their catalytic activity, and they do it without receptor mediation. Using lipid model systems, it has been shown that they are able to enter cells with membranes enriched in acidic phospholipids. Both membrane-interacting and ribosomal-recognition activities are characterised by distinct structural features. Even though the natural function of ribotoxins is not known yet, their production by entomopathogenic fungi has suggested their insecticidal role. After decades of detailed study, the biotechnological potential of ribotoxins in pest control and as antitumour agents is becoming evident.Item Fungal extracellular ribotoxins as insecticidal agents(Insect Biochemistry and Molecular Biology, 2013) Olombrada Sacristán, Miriam; Herrero Galán, Elías; Tello, Daniel; Oñaderra Sánchez, Mercedes; Gavilanes, José G.; Martínez Del Pozo, Álvaro; García Ortega, LucíaFungal ribotoxins were discovered almost 50 years ago as extracellular ribonucleases (RNases) with antitumoral properties. However, the biological function of these toxic proteins has remained elusive. The discovery of the ribotoxin HtA, produced by the invertebrates pathogen H. thompsonii, revived the old proposal that insecticidal activity would be their long searched function. Unfortunately, HtA is rather singular among all ribotoxins known in terms of sequence and structure similarities. Thus, it was intriguing to answer the question of whether HtA is just an exception or, on the contrary, the paradigmatic example of the ribotoxins function. The work presented uses HtA and -sarcin, the most representative member of the ribotoxins family, to show their strong toxic action against insect larvae and cells.- Project number: 326
Item Hacia una Universidad Complutense más diversa: actividades de visibilización del colectivo LGTBI en las Facultades de Químicas y Biológicas(2022) Rodríguez Crespo, José Ignacio; García Ortega, Lucía; Guzmán Pastor, Manuel; Narbona Corral, Javier; Gutiérrez Carmona, Adrián; Arauco Arteche, Iñigo; Ballesteros Sanabria, Laura; Castromil Benito, Estela Soraya; Amigot Sánchez, Rafael; Cueto Remacha, Mateo; Martín Migallón, Guillermo